I don't think this so much a matter of who found what equation, or of
what property is implied by what they said. Einstein reduced special
relativity to the empirical study of how we actually go about measuring
things. This did not require a prior knowledge of Maxwell's equations,
but an observation about how we use light in the empirical *definition*
of time and space coordinates. The MM experiment was not strictly
required, but had light not behaved in the way it does, it is not just
relativity which would be wrong, but we would have no meaningful
definition of the metre, and would not be able to state Maxwell's
equations.

Regards

All that's required is that the Lorentz transformations constitute the
unique solution that satisfies all constraints. And Poincare solved
that problem. The rest is just didactical stuff for human consumption.
It only gives people the illusion they grasp something about it.

Regards

If you meant that Einstein founded the modern way of presenting SRT, I think
that most people will agree.

Regards

Regards

 > >> This did not require a prior knowledge of Maxwell's equations,

It would be unfair to think Poincaré was a mediocre physicist,
too. The way he actually applied and gave form to the PoR for all
physical phenomena advanced by Maxwell in 1877, how he reviewed
and analyzed the existing theories of the electron (by then a
fashionable topic with lots of papers) in the light of his PoR
and how he realized an error in all these theories which led him
to introduce the electron stress in the 1906 paper (even if in
contradiction with the statement in the same paper that all mass
had electromagnetical origin), reveal that he had a very good
understanding of physical phenomena.

The fact he was unable to give the step Einstein did only reveals
Poincaré was human and therefore he wasn't perfect--and saying
Eintein gave only a "baby step" won't help Poincaré either, as
this would imply Poincaré was short-minded, something I strongly
disagree.

http://www-cosmosaf.iap.fr/Poincare-RR3A.htm#demo

Annex 1 of :

http://www-cosmosaf.iap.fr/Poincare-RR3A.htm

Whether we set this invariant equal to "c" we get the SR, but according
to the demo, it is not mandatory.

We would have other physical  theories compliant with PoR with other
values of this invariant ( but I am not sure they would be formaly
different , this invariant beeing the maximum speed, it will play the
part of the speed of light in SR).
Just to notice that, in such a theory, the light would not play the
very special part it does in SR. It would be the physical phenomenon
associated to this "invariant maximum speed" which would play the part.
Just call it "light" and the game is over....

"This just remember me the stoty of the guy who tried to demonstrate
that the Illiad and Odyssey had not been written by Homer but by a guy
who had the same name..".

Note: The purpose of the memo, I wrote about the contribution of
Poincare to SR ( referenced above) , following a "wild" discussion we
had at the SAF, was not to claim that Poincare is the "inventor" of the
SR.

It is just to emphasize how, in a very different way of Einstein, he
tried to find a solution to the crisis of the physics, raised by the MM
experience, especially before and up to the the publication of the
Einstein paper in 1905 ( the details are in the memo).

To the definition of time and metre Poincaré has written 1905 (view my short
notes about history of SR in http://www.soso.ch/wissen/hist/SRT/srt.htm page
498 in [P3]):

" Comment faisons nous nos mesures? En transportant, les uns sur les autres,
des objets regardés comme des solides invariables, répondrat-on d'abord;
mais cela n'est plus vrai dans la théorie actuelle, si l'on admet la
contraction lorentzienne. Dans cette théorie, deux longueurs égales, ce sont
par définition, deux longueurs que la lumière met le même temps à
parcourir."

And consequently  - Poincaré has known, that this only makes sense, if c is
the limiting velocity - he was the first physicist, who was setting c = 1,
as you can see in [P2] (5/11 june 1905) and [P3] (23 july 1905/2 march
1906). This was before Einstein had finished his SR-paper. In [3] Poincaré
also realized that the special Lorentztransformation ist a rotation in the
poincaré/minkowski-spacetime. I think it should be clear from this, that
Poincaré 1905 was very modern. And don't forget: All more philosphical ideas
about space and time came from Poincaré and NOT from Einstein.

But Poincaré was 1905 not sure, if this definition (measuring of lenghts
with "light-time") would be the best definition for all times; Also today
I'm not sure too.

A hint to Poincarés "Lorentz-pressure": It is of course not a pressure
relative to an absolute system (Einsteins Ruhesystem), because such a system
physically ist not prefered in the Lorentztheory and about this point
Poincaré let no doubt in his publications since about 1900; B of a moving
charge also disappears in the "Ruhesystem".

"The formal content of special relativity, however,
is coded into the Lorentz transformations, written by
Lorentz, not by Einstein, and before 1905. So, what
was Einstein's contribution? It was to understand
the physical meaning of the Lorentz transformations.
(And more, but this is what is of interest here). We
could say -admittedly in a provocative manner- that
Einstein's contribution to special relativity has been
the interpretation of the theory, not its formalism:
the formalism already existed." p. 2.

Rovelly states

"Einstein's 1905 paper suddenly clarified the matter by pointing out
the reason for the unease in taking Lorentz transformations
'seriously': the implicit use of a concept (observer-independent time)
inappropriate to describe reality when velocities are high.
Equivalently: a common deep assumption about reality (simultaneity is
observer-independent) which is physically untenable. The unease with
the Lorentz transformations derived from a conceptual scheme in which
an incorrect notion -absolute simultaneity- was assumed, yielding
any sort of paradoxical consequences. Once this notion was removed the
physical interpretation of the Lorentz transformations stood clear, and
special relativity is now considered rather uncontroversial."

Precisely, the abandon of the absolute time and interpretation of LT in
a new mechanical framework with c limiting speed (therefore
relativistic effects observable to high velocities) and t relative was
achieved by Poincaré. It was Poincaré who first introduce the
spacetime (x, ct) concept before Minkoswki did.

I already cited to Poincaré assuring that there is no absolute time.
Now i will cite to Lorentz (1914):

"I had not thought of the straight path leading to them, since I
considered
there was an essential difference between the reference systems x, y,
z, t and x', y', z', t'. In one of them were used - such was my
reasoning - coordinate
axes with a definite position in ether and what could be termed true
time; in the other, on the contrary, one simply dealt with subsidiary
quantities introduced with the aid of a mathematical trick. Thus, for
instance, the variable t' could not be called time in the same sense as
the variable t. Given such reasoning, I did not think of describing
phenomena in the reference
system x', y', z', t' in precisely the same way, as in the reference
system x, y, z, t"

and adds

"I later saw from the article by Poincaré that, if I had acted in a
more systematic manner, I could have achieved an even more significant
simplification. Having not noticed this, I was not able to achieve
total invariance of the equations; my formulae remained cluttered up
with excess terms, that should have vanished. These terms were
too small to influence phenomena noticeably, and by this fact I could
explain their independence of the Earth's motion, revealed by
observations, but I did
not establish the relativity principle as a rigorous and universal
truth. On the contrary, Poincaré achieved total invariance of the
equations of electrodynamics and formulated the relativity postulate
- a term first
introduced by him"

"I am unable to present here all the beautiful results obtained by
Poincaré. Nevertheless let me stress some of them. First, he did not
restrict himself by demonstration that the relativistic transformations
left the form of electromagnetic equations unchangeable. He explained
this success of transformations by the opportunity to present these
equations as a consequence
of the least action principle and by the fact that the fundamental
equation expressing this principle and the operations used in
derivation of the field equations are identical in systems x, y, z, t
and x', y', z', t'."

Poincaré showed that equations were identical in both frames and
formulated the 4D spacetime concept with the invariant ds. For
Poincaré, Lorentz local time was not a mathematical trick, WAS the
"time read from the clocks" [Poincaré (1900) "The theory of Lorentz
and the principle of equal action and reaction"].

Also the Einstein operational definition of time being the reading of a
clock is another of Poincaré achievements.

I do not know basic principle, formalism, postulate, law, concept, or
simlar of SR that was formulated by Einstein like NEW.

"The relativity theory of Poincaré and Lorentz"
                                     Whittaker.

See
http://canonicalscience.blogspot.com/2005/08/what-is-history-of-relat...

for further references and data. New extended version in preparation.

Juan R.

And Newton was a wise man as he only described reality
without trying to *interpret* it in terms of known
phenomena (in his Principia; Optiks is another matter).
Remember: "Hypothesis non fingo", a maxim which shouldn't
be forgotten.

Some of the most important original papers on the way to SR with short
comments in german you find in http://www.soso.ch/wissen/hist/SRT/srt.htm

IMO, his argumentation there was utter nonsense.
In contrast, Lorentz 1904:

"Consequently, the proper relation between the forces and the
accelerations will exist in the two cases, if we suppose that the masses
of all particles are influenced by a translation to the same degree as
the electromagnetic masses of the electrons."

Now that I consider a bold step.

] Now i will cite to Lorentz (1914):
]
] "I had not thought of the straight path leading to them, since I
] considered there was an essential difference between the reference
] systems x, y, z, t and x', y', z', t'. In one of them were used -
] such was my reasoning - coordinate axes with a definite position
] in ether and what could be termed true time; in the other, on the
] contrary, one simply dealt with subsidiary quantities introduced
] with the aid of a mathematical trick. Thus, for instance, the variable
] t' could not be called time in the same sense as the variable t.
] Given such reasoning, I did not think of describing phenomena in
] the reference system x', y', z', t' in precisely the same way, as
] in the reference system x, y, z, t"

I would be grateful if you could give the full reference to this citation,
which I find very interesting because it clearly shows that for Lorentz
himself the transformation bearing his name was *not* relating space-time
measurements of the same event in different inertial frames -- it is a
"mathematical trick" concerning the "subsidiary quantities" x', t'.

Although some people apparently think otherwise, I find it fairly obvious
from reading Lorentz' 1904 article (which the above excerpt seems to be
commenting), that he believes in galilean relativity plus FitzGerald-Lorentz
contraction. I think Poincaré did too: for instance in his 1909 Conference
he explains that a ligth wavefront, spherical in one frame, would *appear*
ellipsoidal in another fame moving with respect to first, because of the
contraction of the measuring rods -- and this is definitely different from
Einstein's prediction that the wavefront would appear spherical in all
inertial frames.

1. Exactly the same title have only the papers of 5. june 1905 and of 23
july 1905

2. The paper of 5 june 1905 is only a relatively long "abstract" of the
SR-paper of 23 july 1905 with *all* most important results of the 23
july-paper for priority reasons - as I think - because Poincaré has known of
course that up to the appearance of the mainpaper in the rendiconti one had
to wait a long time. It seems that Poincaré has written his short note to
C.R. after finishing all calculations (otherwise he would not have been
able to list the correct results including the most important errors of
Lorentz) - but before he had written the full text of his july-paper in a
printable version.

Poincaré and Lorentz NOT assumed different transformation rules for
electromagnetic and mechanical masses: They claimed that all masses (forces)
have to behave in the same manner; Poincaré especially emphasized that this
has to be so if PoR is valid and such sentences you don't find for the first
time 1905, but you can find similar statements of Poincaré already in 1904,
before he had read the article of Lorentz.

" Wir bemerken, daß diese Resultate über die [longitudinale und
transversale] Masse auch für die ponderablen materiellen Punkte gilt
[gelten]; denn ein Punkt kann durch Zufügen einer beliebig kleinen
elektrischen Ladung zu einem Elektron (in unserem Sinne) gemacht werden. "
(view [E1], page 919 in http://www.soso.ch/wissen/hist/SRT/srt.htm)

For me a very dark explanation, *extremely* far from a bold step.

On the other hand: For me this is one of the sentences in Einsteins paper,
which seem me to show that Einstein probably has known - before finsishing
his paper - the articles of Poincaré (and Lorentz), where he could find all
most important results of his own paper. But didactically and in writing
style it remains a master work.